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Introduction to Animal Structure and Function

Chapter 40

Form = FunctionReminds us of the concepts

of evolution and the process which drives it, natural selection.

Physical laws and the environment constrain animal size and shape.

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Form=Function

Often explains convergent evolution as well.

Speedy Swimmers

Exchange with the environment• An animal’s size and shape

have a direct effect on how the animal exchanges energy and materials with its environment.

• Simple animals (as well as unicellular organisms –Protists) have little difficulty in accomplishing this with diffusion.

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Larger more complex animals (with several layers of tissues and complex organ systems) cannot rely on diffusion only to exchange materials with the environment.

As animal complexity evolved, complex organ systems, organs and tissues had to evolve as well to accommodate these exchanges between and animal and its environment.

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Our focus will be on the anatomyand physiology of animals.

Anatomy – is the study of the structure of an organism

Physiology – is the study of the functions an organism performs

Tissue

• An integrated group of cells with a common structure and function

• Each type of tissue is composed of cells with characteristic sizes, shapes and arrangements

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There are four categories of tissues in most animals

1. Epithelial Tissue – sheets of cells that covers the body and lines organs and cavities

Functions: a. Protectionb. Absorptionc. Secretiond. Sensory

Epithelial tissues are classified based upon the number of cell layers and the shape of the cells

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2. Connective Tissue

Functions to support and bind other tissues and organs

In contrast to epithelial tissues which are densely packed, connective tissues are loose aggregations of cells scattered through an extracellular matrix

Many connective tissues produce fibers which are made of protein

• Collagenous fibers – made of collagen; strong fibers

• Elastic fibers – made of protein called elastin; restore shape

• Reticular fibers – made of thin strands of collagen; thin and branched they form a supportive net

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There may also be specialized cells present in connective tissue

• Fibroblasts – secrete the proteins for extracellular fibers

• Macrophages – amoeboid cells that are the “garbage men” cleaning up bacteria and broken cellular fragments by phagocytosis

• Mast cells – release histamine

• Adipose cells – storage of fats

Examples of some types of connective tissues

• Loose Connective tissue – most common in vertebrate’s body, loose weave of all three fiber types– Anchors organs, holds

water, and useful for storage

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• Adipose tissue– Specialized form of loose connective tissue that

stores fat in adipose cells– Functions for energy storage , insulation and

“padding”

• Fibrous (or Dense) Connective tissue – lots of collagen fibers organized into parallel bundles– Tendon and ligaments are examples

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• Cartilage – many collagen fibers with a rubbery matrix of chondroitin sulfate. These are secreted by special cells called chondrocytes– Offers flexible support

• Bone tissue – mineralized connective tissue with a matrix of calcium phosphate secreted by osteocytes– The osteocytes are arranged around a central canal (Haversian

Canal) in concentric rings– These concentric rings of osteocytes are connected by

canaliculi (cytoplasmic extensions of osteocytes)– The central canal, osteocytes, and the CaPO4 matrix make up

the functional unit of bone tissue called and osteon– Functions for rigid support but is not brittle

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• Blood – although a fluid is still a tissue. The extracellular matrix is a water based substance called plasma. The cells suspended in this plasma are :– Erythrocytes (RBC’s)– Leukocytes (WBC’s)– Platelets – fragmets of cells used in clotting process

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3. Nervous Tissue • Senses stimuli and transmits signals in the form of

electrochemical impulses

• Specialized cells called neurons are responsible for the generation of these impulses

4. Muscle Tissue

• Composed of long cells called “fibers”which are capable of contraction

• Three main categories of muscle tissue

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Skeletal – striated appearance

• Voluntary control, attaches to skeletal system for movement and each fibers is multi-nucleated

Smooth Muscle• Lacks striations;

involuntary control (lines digestive tract for example). Spindle shaped fibers. Contracts with less force than skeletal muscle but for longer duration. Each fiber has a single nucleus

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Cardiac Muscle• Found in vertebrate

heart, involuntary, striated but branched fibers with intercalated disks connecting adjacent fibers which relay impulses during a heartbeat